.sub {
    float: left;
    width: 190px;
    margin-left: -100%;
    background-color: red;
}
.main {
    float: left;
    width: 100%;
    background-color: white;
}
.main-wrap {
    margin: 0 230px 0 190px;
}
.extra {
    float: left;
    width: 230px;
    margin-left: -230px;
    background-color: green;
}